Generally, in a system involving a communications device and an information technology (IT, Information Technology) device, a fan is used to help with heat dissipation of the devices. With an increase in network traffic, power consumption of the communications device becomes higher, which requires higher performance of the fan. A rotational speed of the fan reaches over 10,000 RPM. The fan is required to support counter-rotating to prevent intake of dust into the device from affecting service life of the fan, thereby achieving an automatic dust removal function. In addition, generally, an operating environmental condition of an outdoor communications module is adverse, and a variation of a temperature difference in different areas or between day and night is large, which also affects the service life of the fan, and indirectly affects reliability of the device. Therefore, in the system, the fan requires long service life and high reliability, so as to adapt to a more adverse environmental condition, and how to extend the service life of the fan in a current fan condition becomes a major issue currently.
In the prior art, a fan control system is formed by a fan unit, a fan interface, and an external control unit. The fan unit uses a five-wire system counter-rotating fan and is formed by one or more fans. Each fan needs to connect a dedicated five-wire interface connector. The fan acquires an external power supply by using the fan interface. The external system control unit implements rotational speed control on the fan by using a fan interface pulse width modulation (PWM, Pulse Width Modulation) control bus, implements alarm detection on the fan by using a fan rotational speed frequency signal (FG, Frequency Signal) bus of the fan interface, and implements forward and counter-rotating control on the fan by using a fan interface rotation direction control line.
However, the prior art is applicable to a five-wire system fan, and an application interface applicable to a four-wire system fan commonly used in the industry can use only two among the PWM, FG, and rotation direction control buses and cannot be compatible with all functions. Therefore, smooth upgrade cannot be achieved during application of a product on an existing network, and forward and reverse air ducts cannot be compatible without changing fan design.